Construction of a folding box corner,and method of assembly



June 17, 1969 cQJ PIERCE, JR 3,450,330

CONSTRUCTION OF A FOLDING BOX CQRNER, AND METHOD OF ASSEMBLY Filed Dec.21, 1967 Sheet of 4 a7 L3 as INVENTOR. Chesfer J. Pierce, Jr.

ATTORNEY June 17, 1969 c, J, P JR 3,450,330

CONSTRUCTION OF A FOLDING BOX CORNER, AND METHOD OF ASSEMBLY FiledDec/21, 1967 Sheet 2 of 4 I N VENTOR. C/zesfer J Pierce, Jr.

ATTORNEY June 1969 c. J. PIERCE, JR -T 3, ,330

CONSTRUCTION OF A FOLDING BOX CORNER, AND METHOD OF ASSEMBLY Sheet FiledDec. 21. 1967 Fig. 8

INVENTOR C/zesfer J. Pierce; Jr.

ATTORNEY June 17, 1969 c. J. PIERCE, JR

CONSTRUCTION OF A FOLDING BOX CORNER, AND METHOD OF ASSEMBLY Sheet 4 of4Filed Dec. 21, 1967 INVENTOR. C/vesfer J. Pierce, Jr:

ATTORNEY United States Patent US. Cl. 229-33 6 Claims ABSTRACT OF THEDISCLOSURE The present improvements provide a folding box cornerconstruction capable of glueless assembly and provided with an interiorcorner gusset for liquid proofness and increased mechanical rigidity andresistance, particularly to inwardly directed compressive force exerted,for example, during the gluing to the box body walls of flaps on thecover. The ,box body walls are locked together by an exteriorly disposedlock flap articulated to one wall panel and partially inserted in a slotin the other wall panel. The lock flap has a hook formed in it which isof such configuration in relation to the slot that its tip fails toclear the slot unless the upper portion of the wall panel from which itextends is flexed into an angular position with respect to the lowerwall portion, thereby raising the tip sufficiently high to clear theslot. A tab on the lock flap pointing in a general direction opposite tothe hook tip is resiliently snapped past an edge of the slot and acts asa safety catch for the hook preventing disengagement of hook and sloteven under conditions under which the wall panel is flexed.

SPECIFICATION The present invention is directed to improvements in thecorner construction of gluelessly assembled folding boxes, moreparticularly boxes for the packaging of frozen foods, in which a cornergusset is provided to impart liquid proofness to the box body up to acertain level and in which a lock flap is provided above the cornergusset for locking the respective wall panels together.

Frozen food boxes are generally made from paperboard having a coating ofthermoplastic material thereon which makes the board non-absorbent toliquid and even permits heat sealing of the filled box withoutapplication of additional adhesive, provided appropriate techniques areemployed in adhering flaps on the box cover to the sides of the boxbody.

The reliability of the heat seal depends in a large measure on theability of the box body to resist caving-in under the sealing pressureexerted on the cover side flaps from the outside, particularly at thecorners.

Interiorly disposed gusset panels provide the required strength andrigidity at the box corners.

A lock flap is provided at each of the corners above the level to whichthe gusset panels extend. The lock flap is of hook-shaped configurationand is insertable into a slot in the other wall panel. According to thepresent invention the lock flap hook and the slot are so contoured anddimensioned that the hook tip can neither be inserted into the slot norbe withdrawn therefrom unless the wall panel portion from which the flapextends is flexed with respect to the portion of the same wall panelwhich lies adjacent the gusset panels. Such flexing, which must bedeliberate, then raises the hook tip sufiiciently to clear the slot.

A further safety catch tab may be provided on the lock flap, which tabis resiliently snapped past one edge of the slot and extends in adirection generally opposite to the direction of the hook. The tabprevents disengagement of the lock flap from the slot even underconditions of deliberate flexing of the wall panel once the lock isengaged and the safety tab is set.

The security of the lock is of great importance in the automaticpackaging of frozen foods where supervising personnel occasionallyhandle filled, but still open boxes by the upstanding cover panel whilethe boxes are mov-' ing through the machinery. This puts a severe strainon the rearward corner locks, and also causes considerable distortion ofbox panels. The corner locks must not come apart under such conditions,as disengagement of the locks would result in spillage of contents onthe machine and necessitate shutdown of the entire packaging line fromthe box former to the box closer and sealer.

Box corner constructions comprising an interiorly disposed pair ofgusset panels between adjacent wall panels and an exteriorly disposedlock flap of hook-shaped configuration on one of the wall panels andinserta-ble in a slot in the other wall panel are basically known asapplied to re-collapsible open trays. In the known construction theengagement of the hook with the slot depends solely on the depth ofinsertion of the hook. The danger of disengagement of the corner lock isconsiderable, if the trays are picked up or otherwise handled by thewall panel from which the lock flap extends. Rivets and staples areprovided in the known tray construction for the purpose of maintainingcertain gusset portions in a prefolded condition, but these rivets orstaples do not prevent disengagement of the hook.

A corner construction of the known basic type and its method of assemblyare improved according to the present invention in the manner set forthin the characterizing clause of the independent claims appended hereto.

The objects, features and advantages of this invention will appear morefully from the detailed description which follows accompanied bydrawings showing, for the purpose of illustration, a preferredembodiment of the invention. The invention also resides in certain newand original features of construction, combination of elements andmethod steps hereinafter set forth and claimed.

Although the characteristic features of this invention which arebelieved to be novel will be particularly pointed out in the claimsappended hereto, the invention itself, its objects and advantages andthe manner in which it may be carried out may be better understood byreferring to the following description taken in connection with theaccompanying drawings forming a part of it in which:

FIG. 1 is a plan view of a blank of a hinge cover folding box embodyingthe invention;

FIGS. 2, 3 and 4 are isometric views of a corner portion of the blank ofFIG. 1 in successive stages of assembly;

FIG. 5 is an elevational end view of the completed and sealed box;

FIG. 6 is an elevational end view, partly in section, illustrating atool, and its operation, for deflecting a tongue to facilitateengagement of the lock flap, the section being taken on line 6-6 of FIG.7;

FIG. 7 is an elevational end view, partly in section, on line 7-7 of thestructure of FIG. 6;

FIG. 8 is a plan view of the structure shown in FIGS. 6 and 7, portionsbeing shown in section along line 8-8 of FIG. 7; and

FIG. 9 is a plan view of a dovetailed layout of blanks incorporating theinvention, in a large sheet of paperboard.

In the following description and in the claims various details will beidentified by specific names for convenience. The names, however, areintended to be generic in their application. Corresponding referencecharacters refer to corresponding parts in the several figures of thedrawings.

The drawings accompanying, and forming part of, this specificationdisclose certain specific details of construc tion for the purpose ofexplanation of broader aspects of the invention, but it should beunderstood that structural details may be modified in various respectswithout departure from the principles of the invention and that theinvention may be incorporated in other structural forms than shown.

The blank A shown in FIG. 1 may be cut and scored in multiple from largesheets or rolls of paperboard, prefera'bly board bearing a coating of athermoplastic substance at least on the surface which becomes the insideof the box in order to impart moisture resistance to the board. Whenapplying suitable techniques, such coatings permit heat sealing ofportions of the box cover to portions of the box body after filling andclosing of the box.

Design of a representative blank A The blank A comprises a bottom panel11 to which side wall panels 12, 13 and end wall panels 14, 15 arearticulated along bottom fold lines 16, 17, 1'8 and 19, which intersectat corner points 20, 21, 22 and 23.

The wall panels are interconnected at the corners by pairs of gussetpanels which are foldable along diagonal gusset fold lines 24, 25, 26and 27.

Each pair of gusset panels comprises a tall gusset panel 28, 29, 30 and31 articulated to the end wall panels along corner edge lines 32, 33, 34and 35, and a low gusset panel 36, 37, 38 and 39 articulated to the sidewall panels 12, 13 along corner edge lines 40, 41, 42 and 43.

It is thus seen that the corner gussets lie adjacent the four cornerpoints. Remote from the corner points, and adjacent the upper or topedges of the side wall panels, lock flaps 44, 45, 46 and 47 arearticulated to the side wall panels along corner edge lines which arepreferably slightly offset in the direction of the lock flaps and areidentified as lines 140, 141, 142 and 143, respectively.

Internal cuts 48, 49, 50 and 51 form slots in the end wall panels intowhich the lock flaps 44, 45, 46 and 47 may be inserted. In order tofacilitate such insertion, the internal cuts are preferably madeangular, thus defining deflectable tongues 52, 53, 54 and 55 in the endwall panels.

The end portions of the lock flaps are contoured to provide a hook tabportion for hooking into the end of the respective end wall slot orotherwise engaging the slot. The hook tab portions are numbered 56, 57,58 and 59.

The dimensions and disposition of the lock flap end portions in relationto the internal slots in the end walls are such that the distance fromthe corner point (for example 20) to the hook tip (for example 56) isless than the distance from the corner point 20 to the end of therespective internal cut or slot (for example 48), considering that end72 which is nearest the corner point. In FIG. 1 the respective ends arenumbered 72, 73-, 74 and 75.

If, therefore, the wall panels 12 and 14 are folded into uprightposition with respect to the bottom panel 11 and the lock flap 44 isfolded over the outside of the end wall panel 14, and if an attempt weremade to insert the lock flap into the slot, it would be found that thehook tab tip 56 fails to clear the cut 48, therefore resistinginsertion.

If, on the other hand, it were assumed that by some technique the end ofthe lock flap 44 were fully inserted in the slot 48, the hook tab 56would then resist withdrawal of the lock flap because of insufficientclearance for it to slip out of the slot 48.

The hook tab is preferably so oriented as to point towards the mainpanel of the box, considering the box in set up condition.

Preferably-even though not necessarily-the lock flaps are provided witha further tab portion which extends beyond the confines of the internalcut or slot, considering the corner structure assembled. This furthertab portion may be termed a safety catch tab and preferably points in adirection at right angles, or opposite, to the direction in which thehook tab points.

Such safety catch tab portions are shown at 60, 61, 62 and 63 and theirsignificance will become further apparent from FIGS. 5 to 8 later to bedescribed.

A cover panel 64 is articulated to the side wall panel 12 along a coverhinge fold line 65 and cover flaps 66, 67, and 68 extend from the coverpanel along cover flap fold lines 69, 70 and 71.

For the sake of simplification of FIGS. 2 to 4 and 6 to 8, the coverpanel and its flaps are omitted in these figures.

Assembly of blank A into box farm Blank A lends itself to assembly intobox form and to locking of the box corners by a device of theplungerand-die type in which a plunger forces the flat blank into andthrough a die. During the passage into and through the die the cornersare formed and locked.

FIG. 2 and the subsequent figures illustrate the assembly of only onebox corner, it being understood that the other three corners areassembled in the same manner, preferably simultaneously with the onecorner. It will therefore suffice to describe one corner only, whichproceeds as follows:

The end wall panel 15 is folded into substantially upright position withrespect to the bottom panel 11 along main fold line 19. Simultaneously,or slightly later, the wall panel 12 is folded towards an uprightposition. Such folding causes the corner gusset panels to crease alongthe diagonal fold line 27 and move towards the inside of the box asshown in FIG. 2. Substantially simultaneously the lock flap 47 is foldedinto a position at right angles to the wall panel 12.

Due to the presence of the corner gussets and the lock flap 47, the wallpanel 12 develops increasing rigidity and resistance to flexing. Thereremains, however, a line of weakness 76 which lies between the top ofthe gusset panel 39 and the bottom of the lock flap 47 and extendsacross the entire panel 12 to the corresponding point at the oppositecorner. This line of weakness permits flexing of the panel so as to moveits upper panel portion 112 into an angular position with respect to itslower panel portion 212 about the normally unscored line or axis offlexure 76 (see FIG. 3).

In the state shown in FIG. 3, the panel 15 is fully erected, the gussetsare fully folded, the panel 31 has assumed a right-angular position withrespect to panel 15 and the lock flap 47 is folded over the outside ofthe wall panel 15.

The lack of resistance of the panel 12 to flexing along line 76 is takenadvantage of in order to swing the tip of the hook tab 59 into anelevated position, sufficiently elevated to clear the end point 75 ofthe slot 51.

During flexure the tip 59 may be considered as moving on an are aboutthe axis of flexure 76.

At about this moment the internal tongue 55 is flexed outwardly bysuitable manipulation (see FIGS. 6 and 8) permitting the end of the lockflap 47 to enter the slot 51 as the panel 12 is gradually beingflattened out, for example by movement past pressure rollers 77.

The entire end portion of the lock flap 47 enters the slot except in acase where a safety catch tab is provided on the lock flap.

As seen in FIG. 4 the safety catch tab 63 extends beyond the confines ofthe internal slot 51. The tab 63 is of such size that it may be forcedto the inside of the corner by appropriate flexing of the portion of thelock flap from which it extends. Mechanism for this operation isillustrated in FIGS. 6, 7 and 8.

The plunger which moves the blank through the folding die may beequipped in a manner known per se with hooklike extensions or blades 78,one for each corner. These blades are actuated in dependence on theplunger stroke from a normally extended position indicated in solidlines to a retracted position shown in dash-dot lines. In projectedposition the blade 78 bears against the internal tongue 55 and deflectsit toward the outside, thus opening a slot into which the lock flap maybe inserted into a position inwardly of the blade (arrow' 79).

Towards the end of the plunger stroke the extended blades are retracted,thus pulling the safety catch tab 63 to the inside of the box. In thisposition (FIG. 5) not only the hook tip 59 but also the remainder of theend of the lock flap 47 lies on the inside of the box, and the assemblyof the corner is completed.

The box is then filled and is closed by folding the cover panel 64 downon the box body and folding the cover flaps 66, 67 and 68 over, andbonding them to the walls of the box body.

The sealing procedure entails the application of a sealing force on thecover flaps directed to the inside of the box. It is readily seen thatthe panel would tend to cave in under an application of a force F (FIGS.4 and 6) if it were not for the presence of the gusset panels (28, 36 inFIG. 6) which stitfen the box walls and, in addition, provide leakproofness up to a level L.

FIG. 5 illustrates a preferred pattern for adhering the cover flap 67 tothe box body wall 15 along areas 80 and 180 outlined in dash-dot lines.It is readily seen that the rigidity of the areas 80 exists by reason ofthe gusset panels and that the rigidity of the area 180 exists becauseof its proximity to the main fold line 19 along which the bottom panelbaoks up the wall panel 15.

FIG. 9 illustrates a layout of blanks A in multiple in a sheet '81 inwhich the individual blanks are staggered and dovetailed so as to leavea minimum of waste material between blanks. This layout is brought aboutby reducing the height of the cover flaps to one-half the height of thebox.

The height reduction is quite satisfactory, particularly in view of theliquidand dust-tightness of the box body due to the corner gussets.

The slots above the level L through which dust could enter, were it notfor the presence of the cover flaps, are sealed by the cover flaps eventhough their height is reduced.

What is claimed is:

1. Corner construction of a folding box which comprises a bottom panel,two wall panels articulated to said bottom panel along bottom fold linesintersecting at a corner point, said wall panels being interconnected bya pair of interior gusset panels adjacent said corner point, one wallpanel having an exterior lock flap articulated thereto adjacent itsterminal edge and above the respective gusset panel, said lock flapbeing foldable over, and insertable in, an internal slot in the otherwall panel and comprising a hook portion, the point of which is directedtowards the bottom panel when the hook portion is inserted in said slot,characterized in that the distance of the hook tip from the corner pointis less than the distance from that end of the internal cut which isnearest the corner point to the corner point, and that the upper portionof said one wall panel, to which upper portion said lock flaps isarticulated, is flexible relatively to the lower portion of said onewall panel about a line of flexure extending across said first wallpanel from approximately the terminal edge of the gusset panelarticulated to said first Wall panel, the arrangement resulting infailure of the hook tip to clear the end of the slot when said one panelis swung into corner forming position about its bottom fold line in flatcondition, and in freedom of the hook tip to clear the end of theinternal slot when the upper portion of said one wall panel is flexedrelatively to said lower portion to raise the hook point, causing it totravel on an arc of a radius larger than the distance of the end of theslot from the corner point while said one wall panel is in flexedcondition.

2. Corner construction according to claim 1 in which the lock flapcomprises a tab portion which extends beyond said internal slot,prevents that portion of the lock flap on which it is formed frompassing through said slot when inserted therein, said tab being of adimension sufficiently small to pass through said slot to the inside ofthe corner without permanent creasing of the board when forced past theedge of the slot by a force exerted in a direction substantially normalto the surface of Said tab.

3. Corner construction according to claim 1 in which the lock flapcomprises a tab portion which extends beyond said internal slot and iscapable of being snapped from a position overlying the said other panel,past an edge of the slot, into a position underlying said other panel,said tab portion pointing in a direction substantially opposite to saidhook portion.

4. A hinge cover folding box comprising a box body and a hinge coverarticulated to said box body, said box body comprising a main bottompanel, four wall panels articulated thereto, and incorporating at eachof its four corners the corner construction as defined in claim 1; thehinge cover comprising a cover panel articulated to one of the box bodywall panels, and three cover flaps articulated to said cover panel tooverlie the box body wall .panels exclusive of said one of the box bodywall panels, the height of said cover flaps being approximately one-halfthe height of the box body wall panels, considering the box in closedposition.

5. A hinge cover folding box as claimed in claim 4 in which the heightof each of the corner gusset panels, considering the gusset panels incorner forming position, is approximately one-half of the height of thebox body wall panels which dimensioning makes the blank of the box fullydovetailing in a sheet of paperboard in which blanks are laid out inmultiple.

6. In the method of forming an interlocked corner of a folding box,which box comprises a first and a second wall panel articulated to abottom panel along bottom fold lines intersecting at a corner point, thewall panels being interconnected by a pair of gusset panels adjacent thecorner point, one wall panel having a lock flap articulated theretoalong its lateral edge which is to become the edge of the corner, saidlock flap being foldable over, and insertable in an internal slot in,the other wall panel and comprising a hook portion the point of which isdirected toward the bottom panel, considering the corner in assembledcondition, the length of the hook portion being so great that the tip ofthe hook portion fails to clear the internal cut when the one Wall panelis folded in flat condition into upright position With respect to saidbottom panel, the steps of (a) flexing said one wall panel transversely,so as to cause its upper portion to which the lock flap is articulatedto assume temporarily an angular disposition with respect to the lowerportion to which the gusset panels are articulated, said flexing beingof a degree suflicient for the hook tip to clear the internal slot topass the corner inside, and then (b) flattening out said one Wall panelso as to cause its upper and lower portion to lie in substantially thesame plane in which flattened condition the hook tip fails to clear theinternal slot.

